1 62 EVOLUTION, OLD AND NEW. 



callosities are dry and healthy, for they do not come 

 from the constraint of trammels, nor from the burden 

 of a foreign weight, but are the effects only of the 

 natural habits of the animal, which cause it to continue 

 longer seated than in any other position. There are 

 callosities of these pouched monkeys which resemble 

 the double sole of skin which we have ourselves under 

 our feet; this sole is a natural hardness which our 

 continued habit of walking or standing upright will 

 make thicker or thinner according to the greater or 

 less degree of friction to which we subject our feet." * 



This involves the whole theory of Dr. Darwin. 



Wild animals would not change either their food or 

 climate if left to themselves, and in this case they 

 would not vary, but either man or some other enemies 

 have harassed most of them into migrations ; " those 

 whose nature was sufficiently flexible to lend itself to 

 the new situation spread far and wide, while others have 

 had no resource but the deserts in the neighbourhood 

 of their own countries." f 



Since food and climate, and still less man's empire 

 over them, can have but little effect upon wild animals, 

 Buffon refers their principal varieties in great measure 

 to their sexual habits, variations being much less fre- 

 quent among animals that pair and breed slowly, 

 than among those which do not mate and breed more 

 freely. After running rapidly over several animals, 

 and discussing the flexibility or inflexibility of their 

 organizations, he declares the elephant to be the only 

 one on which a state of domestication has produced 

 * Tom. xiv. p. 326, 1766. f Ibid. p. 827. 



